Model systems for NAD ion dehydrogenases have revealed the existence of a kinetically significant intermediate during non-enzymic dihydronicotinamide reductions. Experiments are currently in progress which will define the chemical nature and generality of these intermediates in several non-enzymic dihydronicotinamide reductions, including those catalyzed by metal ions. The rates of association of a series of specific inhibitors of horse liver alcohol dehydrogenase are being studied to determine if interaction at or near the metal ion site limits the rates of formation of the corresponding inactive complex. The inhibitory properties of a series of chelating agents with respect to DNA polymerase are currently being evaluated in the hope that specific inhibitors of these enzymes can be discovered. The ligand binding properties of acetylcholinesterase from electric eel using equilibrium measurements as well as rapid mixing techniques are being studied.